At a dinner reception before the concert, Mr. Dimon thanked his employees for their efforts. While he was in Asia on business during the storm, he said he quickly heard of JPMorgan workers’ volunteer initiatives.

“I am so damn proud of what you did,” he said.

Afterward, the employees — chosen by lottery — nibbled on pigs in blankets and sushi rolls and met with Tyson Chandler of the New York Knicks. But one employee apparently was more interested in an autograph from his boss, coming up to ask Mr. Dimon to sign his ticket. (The chief executive complied.)

Sucking up just in time for bonus season.

And in case you were wondering, here's what Dimon's signature looks like...